1. Field of the Invention
The invention relates to a method which, with the aid of adsorption agents, enables the production of light-colored alkyloligoglycosides and alkylglycosides having alkyl groups with 8 to 24 carbon atoms.
2. Discussion of the Background
Alkyloligoglycosides and alkylglycosides with alkyl groups having 8 to 24 carbon atoms can be prepared partially or completely from many types of raw materials. These alkyloligoglycosides and alkylglycosides are becoming increasingly important, due to their interesting surface active properties combined with very good biodegradability. For use in the home economics and cosmetics sectors, these products must meet stringent esthetic requirements. Therefore methods are sought by which alkyloligoglycosides and alkylglycosides can be produced in aqueous solutions which are transparent and have an attractive color.
For producing alkyloligoglycosides and alkylglycosides with long-chain alkyl groups, one generally first produces alkyloligoglycosides and alkylglycosides with alkyl groups having 1 to 6 carbon atoms. These intermediate products are then converted to the desired alkyloligoglycosides and alkylglycosides by acid-catalyzed transglycosidation, at elevated temperature. However, the products thus produced are dark in color.
According to European Patent No. 165,721, the color of such products can be improved by multistage bleaching with hydrogen peroxide, and can be stabilized by the addition of compounds which liberate sulfur dioxide.
According to European Patent No. 77,167, reducing agents such as hypophosphorous acid or sulfurous acid can be added in the reaction of alcohols with aldoses or ketoses. The color of the alkylglycosides is thereby improved.
Preventive measures are also known. Thus, according to European Patent No. 102,558, one obtains C.sub.3 to C.sub.5 alkyl glucosides of improved color if the glucosidation is carried out in the presence of an alkali salt of a boron acid.
In preparing long-chain alkylsaccharides, according to U.S. Pat. No. 4,465,828, color improvement can be obtained with the aid of hydroxypolycarboxylic acids such as citric acid, tartaric acid, and malic acid.
According to U.S. Pat. No. 4,483,979, coloring factors can be extracted from alkylpolysaccharides. This costly procedure requires anhydrous polar solvents. In addition, part of the alkylpolysaccharides are extracted in the process, along with the colorants.
The known methods of producing alkyloligoglycosides of improved color are cumbersome, require expensive reagents or else do not lead to the desired color qualities.